[1-4] Note about 'Real-Time' expert systems

Many "real-time" expert systems are 'soft' real-time systems, in that
they claim to be fast. A 'hard' real-time system would have features
that guarantee a response within a fixed amount of real-time (e.g.,
bounded computation, not just a fast match-recognize-act cycle).
Systems like G2 use event-driven processing (restricting certain rules
to execute only when specific WM elements change in a particular way)
as a method of limiting forward chaining.